zzj@rac1> EXPLAIN PLAN FOR SELECT * FROM T_USER;
Explained.
zzj@rac1> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------
Plan hash value: 2508602004
----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%cpu)| Time |
----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 23 | 1817 | 4 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| YANG_T | 23 | 1817 | 4 (0)| 00:00:01 |
----------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement (level=2)
12 rows selected.

从下面的查询结果中可以看出使用EXPLAIN PLAN FOR 查看执行计划时oracle是没有执行要查看执行计划的sql 语句的。

PL/sql Developer使用explain plan（F5）功能。